Potentiometer



y 1963 E. H. TUMBUSCH 3,096,493

POTENTIOMETER Filed May 23, 1961 0W4/e0 H Tun/muscle INVENTOR.

A FOR/v5) Patented July 2, 1963 3,096,498 POTEN'IIQMETER Edward H.Tumbusch, Sepulveda, Calif, assignor to Techno-Components Corp,Northridge, Calif. Filed May 23, 1961, Ser. No. 112,026 9 Claims. (Cl.338-162) The present invention relates in general to the field ofelectrical resistors and more particularly relates to a new and novelpotentiometer apparatus.

A potentiometer is basically a variable voltage divider device or,stated differently, it is a resistor which has a variable contact arm sothat any portion of the potential applied between its ends may beselected. An almost infinite variety of applications exist forpotentiometer devices in the electronics field such as, for example,radio, instrumentation, controls, etc. In radio, for example,potentiometer devices are oftentimes used to intercouple succeedingstages or for volume-control purposes. Again by way of example, in theinstrumentation art a potentiometer will oftentimes be used as one ofthe arms in a bridge circuit of a meter.

One of the big problems encountered today in connection withpotentiometers is that of miniaturization. A major effort has been andis still being exerted to substantially reduce the size and complexityof electronic components to meet present and future needs. In keepingwith this effort and because of the large number of uses to which it canbe put, there is a present need for miniaturized potentiometer. Thepresent invention fulfills this need in that it provides a potentiometercontaining fewer parts than prior devices of this type, with the resultthat the potentiometer to be described herein may be more compact, aswell as more mechanically and electrically reliable, than the earlierdevices.

It is, therefore, an object of the present invention to provide apotentiometer containing relatively fewer parts.

It is another object of the present invention to provide a potentiometerthat is relatively more reliable, both mechanically and electrically.The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objects and advantages thereof, will be better understoodfrom the following description considered in connection with theaccompanying drawing in which an embodiment of the invention isillustrated by Way of example. It is to be expressly understood,however, that the drawing is for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe invention.

FIG. 1 is a top view of the resistance element as it is mounted in thepotentiometer casing;

FIG. 2 is a top view of the remaining elements as they are mounted inthe bottom part of the potentiometer casing;

FIG. 3 is a side-view in cross section of the entire potentiometerassembly;

FIG. 4 is a perspective view of a novel wiper element in thepotentiometer of the present invention; and

FIGS. 5 and 6 show in perspective the external construction of thepotentiometer and, in particular, respectively illustrate twoarrangements for mounting and holding the leads in place.

Considering now the drawings, reference is made in particular to FIG. 1wherein is shown a wire-wound v toroidal-shaped potentiometer resistanceelement 10 fixed- 1y mounted on the upper part 11 of the potentiometercasing, a suitably shaped recess being provided in member 11 for theresistance element. The wall forming a boundary for the recess isdesignated 12. The FIG. 1 section of the potentiometer also includes apair of T-shaped connecting pins generally designated 13 and 14, thepins being relatively rigid structurally and bemg mounted in position oncasing member 11. In a sense, connecting pins 13 and 14 resembleordinary nails in that each connecting pin includes a prong-like elementand a head mounted on one end thereof and at right angles thereto. Theprong like element and head for connecting pin 13 are respectivelydesignated 13a and 13b whereas the prong-like element and head forconnecting pin 14 are respectively designated 14a and 14b. Casing member11 also includes a plurality of semicircular open ings 16a, 16b, and160, in which elements 13a and 14a respectively lie. Thus, connectingpins 13 and 14 are held in position by casing member 11 with elements13a and 14a protruding therefrom. A pair of wire leads 17 and 18respectively interconnect the ends of resistance element 10 withconnecting pins 13 and 14, lead 17 being connected at one end to head13b and, therefore, to element 13a, while lead 18 is connected at oneend thereof to head 14b and, therefore, to element 14a. Hence,connecting-pin elements 13a and 14a are electrically connected throughtheir associated heads and wire leads to ends of resistance element 10.

Reference is now made to FIG. 2 wherein is illustrated the potentiometerarrangement in the bottom portion 20 of the potentiometer casing. Asshown therein, the arrangement includes a worm screw 21 whose threadsmesh with the teeth of a gear 22, the worm screw being inserted in atunnel 23 bored into casing 20 at one side thereof. The dimensions oftunnel 23 are such that the worm screw can be easily turned, the latterbeing prevented from moving out of the tunnel by means of a keeper pin24 which extends into a groove 25 circumferentially machined in the bodyportion of the screw. The unthreaded end of worm screw 21 protrudes fromthe potentiometer casing and is slotted, that is, contains a keyway 26,so that the worm screw can be turned with the aid of a screwdriver orother device. Gear 22 is mounted on a hollow cylindrically-shaped boss20a which is centrally located in an upright position on thepotentiometers bottom casing, a pivot 27 being mounted in a verticalposition in the hollow of the boss. Immediately above gear 22 andresting on both the gear and pivot 27 is a wiper mechanism 28, the wipermechanism being held firmly in contact with the gear and pivot by meansof a retaining ring 30. As will be shown later in connection with FIG.3, the retaining ring itself is fastened down by a portion of pivot 27.The arrangement in FIG. 2 also includes a connecting pin generallydesignated 31, this connecting pin also having two parts to it, namely,a prong element 31a and a head 31b. The head is fitted into a slit 32formed in the casing and the prong element rests in the center one ofthree semicircular openings in the casing designated 33a, 33b, and 33c.Needless to say, openings 33a, 33b, and 330 are respectively inregistration with openings 16a, 16b, and Ida in FIG. 1 so that when thearrangement of FIG. 1 is inverted and placed as a lid over thearrangement of FIG. 2, these six semicircular openings will besuperimposed to form three circular openings in the casing through whichthe connectmg pins will extend, the three circular openings thuslyformed together with slit 32 firmly holding the connecting pins inposition. Although it is more clearly presented in FIG. 3, a wire lead34 electrically interconnects head 31b of connecting pin 31 with thebase of pivot 27 Having thus described the two basic units of thepotentiometer as they are shown in FIGS. 1 and 2, it would be Well atthis point to proceed to a description of these two units as they arecombined to form a complete potentiometer assembly, as shown in FIG. 3.However, it is deemed worthwhile to present beforehand a more deaooaaestailed description of wiper mechanism 28 and for this purpose referenceis now made to FIG. 4 wherein the Wiper mechanism is shown. The wipermechanism basically includes three elements, namely an L-shaped element55, an annular shaped disc-like element 36 and a V-shaped element 37.Element 35 has a long side and a short side bent at a right angle to thelong side to form an L shape, the long side having an elongated hole 35atherethrough for reasons that will be more fully explained below.Element 36 is integral with and extends from the short side of element35 and at right angles to it so that element 36 is substantiallyparallel to the long side of element 35. Element 36 also has a circularhole 36a therethrough located beneath elongated hole 35a so that the twoabove said holes have the same center line. As for V-shaped element 37,this element is integral with and extends from element 36 upwardly andaway from the long side of element 35 so that its plane forms an acuteangle with the plane of element 36. Finally, the apex of element 37 isshaped concave downward for reasons that will also be described later.

Reference is now made to FIG. 3 wherein the complete assembly isillustrated. As shown therein, pivot 27 has four major sections, threeof them being cylindrical in shape, one above the other, and the fourthsection being conical in shape and uppermost on the pivot. Morespecifically, a bottommost section has the widest cross-sectionaldiameter, the intermediate cylindrical section has the narrowestcross-sectional diameter, and the third and uppermost cylindricalsection has a cross-sectional diameter that is intermediate the previoustwo. Integral with and extending upwards from the third cylindricalsection is the conical-shaped section. Pivot 2.7 is firmly held inposition both by casing 20 and boss 20a, the pivot being cemented to thecasing at its base whereat may also be found a keyway 38 into which oneend of wire lead 34- is inserted for interconnecting the pivot with pin31. Gear 22 is mounted on boss Ztla and rests on and is supported by theboss. Immediately above gear 22 is mounted wiping mechanism 28,annular-shaped element 36 of the wiper mechanism resting directly on thegear and the long side of L-shaped element 35 resting directly on theconical-shaped section of the pivot. Thus, since element 36 fits aroundthe intermediate cylindrical sec tion of pivot 27, the reason forcircular hole 36a is now self-evident. Likewise, the reason for hole 35ain element 35 is now also obvious in that the apex of the conical-shapedsection of pivot 27 extends upwards through hole 35a which is purposelyelongated to provide a sufficient tolerance so that element 35 willfully rest on this pivot section, thereby achieving good mechanical andelectrical contact between the parts. Inserted between element 36 of thewiping mechanism and the third cylindrical-shaped section of pivot 27 isretaining ring 30 which, as its name implies, is used to maintain thewiping mechanism firmly in position on the pivot. With respect to thewiping mechanism, it should be noted that when the potentiometer iscompletely assembled as is shown in FIG. 3, V-shaped element 37 ispushed downward by resistance element until element 37 lies in the sameplane as element 36. As a result, a spring action is produced which hasthe effect of forcing the apex portion 37a of the wiping mechanism upand against resist- V ance element 10, thereby obtaining good electricalcontact between the wiper mechanism and the resistance element.

In operation, the turning of Worm screw 21 causes gear 22 to rotateabout pivot 27. In turn, wiper mechanism 28, which is firmly locked togear 22 by retaining ring 30, also rotates about the pivot, apex portion37a thereby sliding along resistance element 10. In this way, anyportionof the over-all voltage applied to the ends of the resistanceelement through connecting pins 13 and 14 may be tapped, the voltagethusly tapped being applied to connecting pin 31.

Slight modifications of the potentiometer described above are shown inFIGS. 5 and 6. More specifically, as modified, relatively rigid pins 13,M, and 31 are replaced by highly flexible wire leads 46, 41 and 42.However, in order to prevent these wire leads from being torn loose, asis often the case among potentiometer devices in the prior art, theorifices formed by easing members 11 and 2t) and through which the Wireleads enter the casing to connect with the potentiometer assembly are ofslightly smaller diameter than the leads themselves. As a result, casingmembers 11 and 20 press against the wire leads and thereby help tofirmly keep them in place. In this way, too, therefore, thepotentiometer of the present invention is more mechanically reliable.

Having thus described the invention, what is claimed as new is: I

l. A potentiometer, the internal structure of said p otentiometercomprising: a circular resistance member non-rotatably fixed inposition; a shaft-like pivot member immovably mounted along the axis ofsaid resistance element; a wiper mechanism mounted on said pivot memberand rotatable thereabout, said Wiper mechanism being in directelectrical contact with said resistance and pivot members; input meansfor applying a potential difierence between the ends of said resistancemember; output means electrically connected to said pivot member fordeveloping an output potential corresponding to the point of contactbetween said wiper mechanism and said resistance member; and means forrotating said wiper mechanism to selectively obtain difierent points ofcontact between said mechanism and said resistance element.

2. A potentiometer, the internal structure of said p tentiometercomprising: a circular resistance member non-rotatably fixed inposition; a shaft-like pivot member immovably mounted along the axi ofsaid resistance element; a gear mounted for rotation around said pivotmember; a Wiper mechanism rotatably mounted on said pivot member andmechanically coupled to said gear, said wiper mechanism being in directelectrical contact with said resistance and pivot members; a worm screwfor rotating said gear in order to rotate said wiper mechanism, saidwiper mechanism thereby being brought into contact with ditterent pointson said resistance member; input means for applying a potentialdifference between the ends of said resistance member; and output meanselectrically connected to said pivot member for developing an outputpotential corresponding to the point of contact between said wipermechanism and said resistance element.

3. In a potentiometer, apparatus comprising: a hollow structure forhousing the potentiometer; a circular resistance element rigidly mountedin the hollow of said structure on one surface thereof; a shaft-likepivot member rigidly mounted in the hollow of said structure on thesurface facing said one surface and along the axis of said resistanceelement, said pivot member including first, second and third cylindricalsections and a conical section one above the other in the order named,said first and second sections respectively having the largest andsmallest cross-sectional diameters and said third section having across-sectional diameter that is intermediate said other two; a J-shapedwiper mechanism respectively having a pair of co-lined openings throughthe opposite sides thereof, said pivot member extending through saidopenings in such a manner that the short side of said wiper mechanismrests on the conical section of said pivot member and is in electricalcontact therewith and the long side of said mechanism rings the secondsection of said pivot member, whereby said mechanism is rotatable aboutsaid pivot member, the free end of the long side of said Wiper mechanismbeing in electrical contact with said resistance element; first meansfor holding said Wiper mechanism on said pivot member and in electricalcontact with said resistance element; and second means for rotating saidwiper mechanism.

enemas 4. The potentiometer apparatus defined in claim 3 wherein saidsecond means includes a gear rotatably mounted in the hollow of saidstructure on the surface facing said one surface, said pivot memberprojecting axially through the center thereof; a worm screw for rotatingsaid gear, said screw being mounted on said structure and through a wallthereof to couple with said gear; and a retaining ring for fasteningsaid wiper mechanism to said gear, whereby the rotation of said gearcauses said wiper mechanism to rotate.

5. The apparatus defined in claim 3, said apparatus further includingfirst and second connecting pins electrically connected to the ends ofsaid resistance element, said first and second connecting pins extendingthrough a Wall of said structure and rigidly held in position thereby;and a third connecting pin electrically connected to said pivot memberat the base thereof, said third connecting pin extending through a wallof said structure and rigidly held in position thereby.

6. The potentiometer apparatus defined in claim 4, said apparatusfurther including first and second connecting pins electricallyconnected to the ends of said resistance element, said first and secondconnecting pins extending through a wall of said structure and rigidlyheld in position thereby; and a third connecting pin electricallyconnected to said pivot member at the base thereof, said thirdconnecting pin extending through a wall of said structure and rigidlyheld in position thereby.

7. A potentiometer, the internal structure of said potentiometercomprising: a rigidly mounted circular resistance element; a shaft-likepivot member rigidly mounted perpendicular to and along the axis of saidresistance element, said pivot member including first, second and thirdcylindrical sections and a conical section one above the other in theorder named, said first and second sections respectively having thelargest and smallest cross-sectional diameters and said third sectionhaving a cross-sectional diameter that is intermediate said other two; awiper mechanism having an L-shaped section, an annular section integralwith and extending from the small side of said L-shaped section parallelto the long side thereof, and a V-shaped section integral with andnormally extending at an angle from said annular section in a directionaway from said long side, the apex of said V- shaped section beingshaped concavely and opening in a direction away from said resistanceelement, said wiper mechanism respectively having a pair of co-linedopenings through said L-shaped and annular sections, said Wipermechanism being mounted on said pivot member in such a manner than saidpivot member extends through said openings with the long side of saidL-shaped section resting on the conical section of said pivot member andsaid annular section ringing the second section thereof, whereby saidmechanism is rotatable about and in electrical contact with said pivotmember, the apex of said \'-shaped section being pressed against saidresistance element which pushes said V-shaped section out of its normalposition for good electrical contact therewith; input means for applyinga potential difference between the ends of said resistance element;output means electrically connected to said pivot member for developingan output potential corresponding to the point of contact between saidwiper mechanism and said resistance element between the ends thereof;and means for rotating said wiper mechanism to selectively obtaindifferent points of contact between said mechanism and said resistanceelement.

8. The potentiometer structure defined in claim 7 wherein said pivotmember has a slot at the base thereof, said output means being insertedin said slot for electrical connection with said pivot member.

9. The potentiometer structure defined in claim 7 wherein said meansincludes a gear mounted so as to encircle said pivot member androtatable thereabout; a worm screw for rotating said gear; and aretaining ring for fixedly coupling the annular section of said wipermechanism to said gear.

References Cited in the file of this patent UNITED STATES PATENTS2,561,116 I-Iof July 17, 1951 2,887,554- Smith et al. May 19, 19592,968,015 Blanco Jan. 10, 1961

1. A POTENTIOMETER, THE INTERNAL STRUCTURE OF SAID POTENTIOMETERCOMPRISING: A CIRCULAR RESISTANCE MEMBER NON-ROTATABLY FIXED INPOSITION; A SHAFT-LIKE PIVOT MEMBER IMMOVABLY MOUNTED ALONG THE AXIS OFSAID RESISTANCE ELEMENT; A WIPER MECHANISM MOUNTED ON SAID PIVOT MEMBERAND ROTATABLE THEREABOUT, SAID WIPER MECHANISM BEING IN DIRECTELECTRICAL CONTACT WITH SAID RESISTANCE AND PIVOT MEMBERS; INPUT MEANSFOR APPLYING A POTENTIONAL DIFFERENCE BETWEEN THE ENDS OF SAIDRESISTANCE MEMBER; OUTPUT MEANS ELECTRICALLY CONNECTED TO SAID PIVOTMEMBER FOR DEVELOPING AN OUTPUT POTENTIAL CORRESPONDING TO THE POINT OFCONTACT BETWEEN SAID WIPER MECHANISM AND SAID RESISTANCE MEMBER; ANDMEANS FOR ROTATING SAID WIPER MECHANISM TO SELECTIVELY OBTAIN DIFFERENTPOINTS OF CONTACT BETWEEN SAID MECHANISM AND SAID RESISTANCE ELEMENT.